Journal of the Plainsong & Mediaeval Music Society volume 6 (1983), page 40, column 2, paragraph 2, second sentence should read:

“She points out that Ordo romanus I and its relatives (III–VII, XV) present the Agnus Dei as a chant accompanying the fraction, often stating that it should be continued until the fraction is completed; Ordines XVII, IX, and X, which are of east-Frankish provenance, state that it should be sung during communion.”